Bright Yellow Ragwort flowering in the Wildflower Meadow at the bottom of the site...

At least 30 insect species (and 14 fungi species) are entirely reliant on Ragwort, and about a third of the insects are scarce or rare. Ragwort is also an important nectar source for hundreds of species of butterflies, bees, moths, flies and other invertebrates, helping to support populations in the UK countryside.
Although Ragwort (Senecio jacobaea) can be a problem for some horses and their owners, it is an extremely important plant in the British countryside and on urban waste ground for the number of insect species it supports. At least 77 invertebrate species have been recorded eating Ragwort leaves, or living in the stems and flowers. About 52 of these are known to regularly feed on Ragwort and, more importantly, 30 species are entirely dependant on Ragwort, the Cinnabar moth for example, a beautiful macro moth. About a third of these 30 species are scarce or rare.
Ragwort is also an important nectar source for over one hundred species (117, says English Nature) of butterflies (Small copper is just one), bees, moths, flies and other invertebrates, helping to maintain insect populations generally in the UK countryside.

Text by Buglife UK

Follow this link for more interested facts about Ragwort

Ragwort : weed or wildflower?

Ragwort is poisonous to horses, damaging the liver when eaten. The toxic effect builds up over time, causing irreparable damage. This means that your horse will get just as ill from eating small amounts of ragwort over a long period of time as it would do from eating a large quantity in one go. 

Visit : World Horse Welfare